Process for manufacturing cellulose fibres

ABSTRACT

Solvent-spun cellulose fibers having a reduced tendency to fibrillate are produced by treating the fibers with one or more compounds from the group of the 
     (A) N-methylol ethers of carboxamides, urethanes, ureas and aminotriazines, 
     (B) N-alkyl-mono- or polysubstituted cyclic hydroxy- or alkoxy-ethyleneureas, 
     (C) hydrophilic modified polyisocyanates, and 
     (D) mixtures of polyurethanes with isocyanates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel process for producingsolvent-spun cellulose fibers having a reduced tendency to fibrillate bytreating the fibers with certain reactive compounds.

2. Discussion of the Background

GB-A-2 043 525 discloses the production of cellulose fibers by spinninga solution of cellulose in a suitable solvent, for example an N-oxide ofa tertiary amine, such as N-methylmorpholine N-oxide. In such a spinningprocess, the cellulose solution is extruded through a suitable die andthe resulting fiber precursor is washed in water and thereafter dried.Such fibers are referred to as solvent-spun fibers.

Such solvent-spun cellulose fibers have many application advantages, buttend to fibrillate, i.e. to break up into very fine fibrils, which canlead to problems with the textile processing of cellulose fibers.

WO-A-92/07124 recommends solving this problem by treating the cellulosefibers with an aqueous solution or dispersion of a polymer having amultiplicity of cationically ionizable groups, for example apolyvinylimidazoline.

Furthermore, EP-A-538 977 teaches the use of compounds having from 2 to6 functional groups capable of reacting with cellulose, for exampleproducts based on dichlorotriazine, for this purpose.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel process forproducing solvent-spun cellulose fibers having a reduced tendency tofibrillate on the basis of different chemical defibrillating reagents.

We have found that this object of producing solvent-spun cellulosefibers having a reduced tendency to fibrillate is advantageouslyachieved by a process which comprises treating the fibers with one ormore compounds from the group of the

(A) N-methylol ethers of carboxamides, urethanes, ureas andaminotriazines,

(B) N-alkyl-mono- or polysubstituted cyclic hydroxy- oralkoxy-ethyleneureas,

(C) hydrophilic modified polyisocyanates, and

(D) mixtures of polyurethanes with isocyanates.

In a preferred embodiment, compounds (A) comprise N-methylol ethers ofthe general formula I ##STR1## where R¹ is C₁ -C₁₀ -alkyl with orwithout interruption by unadjacent oxygen atoms,

R² is hydrogen, CH₂ OR¹ or a C₁ -C₈ -alkyl radical with or withouthydroxyl and/or C₁ -C₄ -alkoxy substitution and with or withoutinterruption by unadjacent oxygen atoms and/or C₁ -C₄ -alkyl-bearingnitrogen atoms, and

R³ is hydrogen, C₁ -C₁₀ -alkyl, C₁ -C₁₀ -alkoxy with or withoutinterruption by unadjacent oxygen atoms, or the group (--NR² --CH₂ OR¹),

or else R² and R³ form a five- or six-membered ring and if R³ =(--NR²--CH₂ OR¹), moreover, two such rings may be fused together via thecarbon atoms on the R² radicals a-disposed to the amide nitrogens toform a bicyclic system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The N-methylol ethers I are readily obtainable by conventional reaction,usually in aqueous solution, of the corresponding N-methylol compoundsof the general formula II ##STR2## with alcohols of the general formulaIII

    R.sup.1 --OH.                                              (III)

The radical R¹ is a C₁ -C₁₀ -alkyl group with or without interruption byunadjacent oxygen atoms, such as --CH₂ CH₂ OCH₃, --CH₂ CH₂ OCH₂ CH₃ or--CH₂ CH₂ OCH₂ CH₂ OCH₃. Further examples of R¹ are n-butyl, isobutyl,sec-butyl, tert-butyl, n-pentyl, n-hexyl, 2-ethylhexyl and2-methoxyethyl; of particular interest are the C₁ -C₃ -alkyl groupsethyl, n-propyl, isopropyl and especially methyl.

The radical R² is hydrogen, CH₂ OR¹ or, in particular, a C₁ -C₈ -alkylradical with or without hydroxyl and/or C₁ -C₄ -alkoxy substitution andwith or without interruption by unadjacent oxygen atoms and/or C₁ -C₄-alkyl-bearing nitrogen atoms.

The radical R³ is hydrogen, C₁ -C₁₀ -alkyl, C₁ -C₁₀ -alkoxy with orwithout interruption by unadjacent oxygen atoms or, in particular, thegroup (--NR² --CH₂ OR¹).

The process of this invention is particularly effective with thoseN-methylol ethers I where R² and R³ form a five- or six-membered ring.If R³ =(--NR² --CH₂ OR¹), moreover, two such rings may be fused togethervia the carbon atoms on the R² radicals α-disposed to the amidenitrogens to form a bicyclic system.

Examples of N-methylol ethers I which can be used in the process of thisinvention are:

amides of C₁ -C₁₁ -carboxylic acids, for example formic acid, aceticacid, propionic acid, butyric acid or valeric acid, which carry one ortwo CH₂ OR¹ groups on the nitrogen,

carbamates having C₁ -C₁₀ -alkyl groups in the ester moiety which may beinterrupted by unadjacent oxygen atoms, for example methyl, ethyl,n-propyl, isopropyl, 2-methoxyethyl or n-butyl, which carry two CH₂ OR¹groups on the nitrogen,

urea having from 1 to 4 CH₂ --OR¹ groups on the nitrogen atoms,

cyclic ethyleneureas of the general formula Ia ##STR3## where theradicals X are different or preferably identical and each is hydrogen,hydroxyl or C₁ -C₄ -alkoxy, for example methoxy or ethoxy,

cyclic propyleneureas of the general formula Ib ##STR4## where Y is CH₂,CHOH, C(CH₃)₂, an oxygen atom or a C₁ -C₄ -alkyl-bearing nitrogen atom,and Z is hydrogen or a C₁ -C₄ -alkoxy group, for example methoxy orethoxy,

bicyclic glyoxal diureas of the general formula IC ##STR5## bicyclicmalonodialdehydediureas of the general formula Id ##STR6##

In a further preferred embodiment, compounds (A) comprise melaminederivatives of the general formula IV ##STR7## where the radicals A areidentical or different and each is hydrogen or CH₂ OR¹, subject to theproviso that at least one of the radicals A is CH₂ OR¹ and R¹ is asdefined above.

The melamine derivatives IV are readily obtainable by conventionalreaction, usually in aqueous solution, of the correspondingN-methylolmelamines of the general formula V ##STR8## where the Aanalogs B are each hydrogen or CH₂ OH, with alcohols of the generalformula III.

Examples of melamine derivatives which can be used in the process ofthis invention are methoxymethylmelamine, bis(methoxymethyl)melamine,tris(methoxymethyl)melamine, tetrakis(methoxymethyl)melamine,pentakis(methoxymethyl)melamine and hexakis(methoxymethyl)melamine andalso the analogous ethoxymethyl and isopropyloxymethyl compounds.

Compounds (A) are known in the textile field as crosslinkers in thelow-aldehyde resin finishing of cellulosic textile materials.

In a further preferred embodiment, compounds (B) comprise cyclichydroxy- or alkoxy-ethyleneureas of the general formula VI ##STR9##where R⁴ and R⁵ are each hydrogen or C₁ -C₃ -alkyl, with the provisothat at least one of the radicals R⁴ - and R⁵ is C₁ -C₃ -alkyl, and R⁶and R⁷ are each hydrogen or C₁ -C₄ -alkyl.

Compounds (B) are known in the textile field as crosslinkers in thealdehyde-free resin finishing of cellulosic textile materials.

The hydrophilic modified polyisocyanates (C) are generally used in theprocesses of the invention in the form of aqueous dispersions which areessentially free from organic solvents and further emulsifiers

The hydrophilic modified polyisocyanates to be used according to thisinvention are based on customary diisocyanates and/or customary higherfunctional polyisocyanates having an average NCO functionality of from2.0 to 4.5. These components can be present alone or mixed.

Examples of customary diisocyanates are aliphatic diisocyanates such astetramethylene diisocyanate, hexamethylene diisocyanate(1,6-diisocyanatohexane), octamethylene diisocyanate, decamethylenediisocyanate, dodecamethylene diisocyanate, tetradecamethylenediisocyanate, trimethylhexane diisocyanate or tetramethylhexanediisocyanate, cycloaliphatic diisocyanates such as 1,4-, 1,3- or1,2-diisocyanatocyclohexane, 4,4'-di(isocyanato-cyclohexyl) methane,1-isocyanato-3,3,5-trimethyl-5-(isocyanato- methyl) cyclohexane(isophorone diisocyanate) or 2,4- or2,6-diisocyanato-1-methylcyclohexane and also aromatic diisocyanatessuch as 2,4- or 2,6-tolylene diisocyanate, tetramethylxylylenediisocyanate, p-xylylene diisocyanate, 2,4'- or4,4'-diisocyanatodiphenylmethane, 1,3- or 1,4-phenylene diisocyanate,1-chloro-2,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate,diphenylene 4,4'-diisocyanate, 4,4'-diisocyanato-3,3'-dimethyldiphenyl,3-methyldiphenylmethane 4,4'-diisocyanate or diphenyl ether4,4'-diisocyanate. It is also possible for mixtures of the diisocyanatesmentioned to be present. Preference is given among these to aliphaticdiisocyanates, in particular to hexamethylene diisocyanate andisophorone diisocyanate.

Suitable customary higher functional polyisocyanates are for exampletriisocyanates such as 2,4,6-triisocyanatotoluene or2,4,4'-triisocyanatodiphenyl ether or the mixtures of di-, tri- andhigher polyisocyanates which are obtained by phosgenation ofcorresponding aniline/formaldehyde condensates and are methylene-bridgedpolyphenyl polyisocyanates.

Of particular interest are customary aliphatic higher functionalpolyisocyanates of the following groups:

(a) isocyanurato-containing polyisocyanates of aliphatic and/orcycloaliphatic diisocyanates. Particular preference amongst these isgiven to the corresponding isocyanato-isocyanurates based onhexamethylene diisocyanate and isophorone diisocyanate. The presentisocyanurates are in particular simple trisisocyanatoalkyl ortriisocyanatocycloalkyl isocyanurates which are cyclic trimers of thediisocyanates, or mixtures with their higher homologs having more thanone isocyanurate ring. The isocyanatoisocyanurates generally have an NCOcontent of from 10 to 30% by weight, in particular of from 15 to 25% byweight, and an average NCO functionality of from 2.6 to 4.5.

(b) Uretdione diisocyanates having aliphatically and/orcycloaliphatically bound isocyanate groups, preferably derived fromhexamethylene diisocyanate or isophorone diisocyanate. Uretdionediisocyanates are cyclic dimerization products of diisocyanates.

(c) Biureto-containing polyisocyanates having aliphatically boundisocyanate groups, in particular tris(6-isocyanatohexyl) biuret or itsmixtures with its higher homologs. These biureto-containingpolyisocyanates generally have an NCO content of from 18 to 25% byweight and an average NCO functionality of from 3 to 4.5.

(d) Urethano- and/or allophanato-containing polyisocyanates withaliphatically or cycloaliphatically bound isocyanate groups, asobtainable for example by reacting excess amounts of hexamethylenediisocyanate or isophorone diisocyanate with simple polyhydric alcoholssuch as trimethylolpropane, glycerol, 1,2-dihydroxypropane or mixturesthereof. These urethano- and/or allophanato-containing polyisocyanatesgenerally have an NCO content of from 12 to 20% by weight and an averageNCO functionality of from 2.5 to 3.

(e) Oxadiazinetriono-containing polyisocyanates, preferably derived fromhexamethylene diisocyanate or isophorone diisocyanate. Suchoxadiazinetriono-containing polyisocyanates are preparable fromdiisocyanate and carbon dioxide.

(f) uretoneimine-modified polyisocyanates.

For the use according to the present invention, particular preference isgiven to aliphatic diisocyanates and aliphatic higher functionalpolyisocyanates.

The disclosed diisocyanates and/or higher functionalized polyisocyanatesare converted into nonionically hydrophilic modified polyisocyanates,which are particularly preferred for the use according to the presentinvention, by reaction with NCO-reactive compounds containinghydrophilicizing structural elements with nonionic groups or with polargroups which cannot be converted into ionic groups. In this reaction,the diisocyanate or polyisocyanate, as the case may be, is present instoichiometric excess in order that the resulting hydrophilic modifiedpolyisocyanate may still contain free NCO groups.

Suitable for use as such NCO-reactive compounds with hydrophilicizingstructural elements are in particular hydroxyl-terminated polyethers ofthe general formula VII

    R.sup.8 --E--(DO).sub.n --H                                (VII)

where

R⁸ is C₁ -C₂₀ -alkyl, in particular C₁ -C₄ -alkyl, or C₂ -C₂₀ -alkenyl,cyclopentyl, cyclohexyl, glycidyl, hydroxyethyl, phenyl, tolyl, benzyl,furfuryl or tetrahydrofurfuryl,

E is sulfur or in particular oxygen,

D is propylene or especially ethylene, including in particularblock-mixed ethoxylated and propoxylated compounds, and

n is from 5 to 120, in particular 10 to 25.

The use of nonionically hydrophilic modified polyisocyanates whichcontain the polyethers VII therefore also constitutes a preferredembodiment.

These are particularly preferably C₁ -C₄ -alkanol-initiated ethyleneoxide or propylene oxide polyethers having average molecular weightsfrom 250 to 7000, in particular from 450 to 1500.

It is also possible to first react the disclosed diisocyanates and/orhigher functionalized polyisocyanates with a deficiency ofhydroxyl-terminated polyesters, of other hydroxyl-terminated polyethers,or of polyols, for example ethylene glycol, trimethylolpropane orbutanediol, to form prepolymers and then react these prepolymerssubsequently or else simultaneously with the polyethers VII indeficiency to form the hydrophilic modified polyisocyanates having freeNCO groups.

It is also possible to prepare nonionically hydrophilic modifiedpolyisocyanates from diisocyanate or polyisocyanate and polyalkyleneglycols of the formula HO--(DO)_(n) --H, where D and n are each asdefined above. In this reaction, the two terminal OH groups of thepolyalkylene glycol both react with isocyanate.

The recited types of nonionically hydrophilic modified polyisocyanatesare more particularly described in DE-A 24 47 135, DE-A 26 10 552, DE-A29 08 844, EP-A 0 13 112, EP-A 019 844, DE-A 40 36 927, DE-A 41 36 618,EP-B 206 059, EP-A 464 781 and EP-A 516 361.

The disclosed diisocyanates and/or higher functionalized polyisocyanatesare converted into anionically hydrophilic modified polyisocyanates byreaction with NCO-reactive compounds containing hydrophilicizing anionicgroups, in particular acid groups such as carboxyl groups, sulfonic acidgroups or phosphonic acid groups. In this reaction, the diisocyanate orpolyisocyanate is present in stoichiometric excess in order that theresulting hydrophilic modified polyisocyanate may still contain free NCOgroups.

Suitable NCO-reactive compounds with anionic groups include inparticular hydroxycarboxylic acids such as 2-hydroxyacetic acid,3-hydroxypropionic acid, 4-hydroxybutyric acid or hydroxypivalic acidand 2,2,2-tris- and also 2,2-bis-(hydroxymethyl)alkanoic acids, forexample 2,2-bis(hydroxymethyl)acetic acid,2,2-bis-(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyricacid, or 2,2,2-tris(hydroxymethyl)acetic acid. The carboxyl groups canbe partly or wholly base-neutralized to be present in a water-soluble orwater-dispersible form. The base used here is preferably a tertiaryamine, which is known to be inert toward isocyanate.

The disclosed diisocyanates and/or higher functionalized polyisocyanatescan also be reacted with a mixture of nonionically hydrophilic-modifyingand anionically hydrophilic-modifying compounds which are added insuccession or simultaneously, for example with a deficiency of thepolyethers VII and the disclosed hydroxycarboxylic acids.

The recited types of anionically hydrophilic modified polyisocyanatesare more particularly described in DE-A 40 01 783, DE-A 41 13 160 andDE-A 41 42 275.

The disclosed diisocyanates and/or higher functionalized polyisocyanatesare converted into cationically hydrophilic modified polyisocyanates byreaction with NCO-reactive compounds containing chemically built-inalkylatable or protonatable functions to form a cationic center. Thesefunctions are in particular tertiary nitrogen atoms, which are known tobe inert toward isocyanate and to be readily quaternizable orprotonatable. In the reaction of diisocyanate or polyisocyanate withthese NCO-reactive compounds, the former are present in excess in orderthat the resulting hydrophilic modified polyisocyanate may still containfree NCO groups.

Suitable such NCO-reactive compounds with tertiary nitrogen atoms arepreferably aminoalcohols of the general formula VIII ##STR10## where R⁹and R¹⁰ are each linear or branched C₁ -C₂₀ -alkyl, in particular C₁ -C₅-alkyl, or are together combined with the nitrogen atom into a five- orsix-membered ring which may additionally contain an oxygen atom or atertiary nitrogen atom, in particular a piperidine, morpholine,piperazine, pyrrolidine, oxazoline or dihydrooxazine ring, in which casethe radicals R² and R³ may additionally carry hydroxyl groups, inparticular one hydroxyl group each, and

R¹¹ is C₂ -C₁₀ -alkylene, in particular C₂ -C₆ -alkylene, which can belinear or branched.

Suitable aminoalcohols VIII are in particular N-methyldiethanolamine,N-methyldi(iso)propanolamine, N-butyldiethanolamine,N-butyldi(iso)propanolamine, N-stearyldiethanolamine,N-stearyldi(iso)propanolamine, N,N-dimethylethanolamine,N,N-dimethyl(iso)propanolamine, N,N-diethylethanolamine,N,N-diethyl(iso)propanolamine, N,N-dibutylethanolamine,N,N-dibutyl(iso)propanolamine, triethanolamine, tri(iso)propanolamine,N-(2-hydroxyethyl)morpholine, N-(2-hydroxypropyl)morpholine,N-(2-hydroxyethyl)piperidine, N-(2-hydroxypropyl)piperidine,N-methyl-N'-(2-hydroxyethyl)piperazine,N-methyl-N'-(2-hydroxypropyl)piperazine,N-methyl-N'-(4-hydroxybutyl)piperazine, 2-hydroxyethyloxazoline,2-hydroxypropyloxazoline, 3-hydroxypropyloxazoline,2-hydroxyethyldihydrooxazine, 2-hydroxypropyldihydrooxazine or3-hydroxypropyldihydrooxazine.

Suitable such NCO-reactive compounds with tertiary nitrogen atomsfurther include preferably diamines of the general formula IXa or IXb##STR11## where R⁹ to R¹¹ are each as defined above and R¹² is C₁ -C₅-alkyl or is combined with R² into a five- or six-membered ring, inparticular into a piperazine ring.

Suitable diamines IXa are in particular N,N-dimethylethylenediamine,N,N-diethylethylenediamine,N,N-dimethyl-1,3-diamino-2,2-dimethylpropane,N,N-diethyl-1,3-propylenediamine, N-(3-aminopropyl)morpholine,N-(2-aminopropyl)morpholine, N-(3-aminopropyl)piperidine,N-(2-aminopropyl)piperidine, 4-amino-1-(N,N-diethylamino)pentane,2-amino-1-(N,N-dimethylamino)propane,2-amino-1-(N,N-diethylamino)propane or2-amino-1-(N,N-diethylamino)-2-methylpropane.

Suitable diamines IXb include in particularN,N,N'-trimethylethylenediamine, N,N,N'-triethylethylenediamine,N-methylpiperazine or N-ethylpiperazine.

Further usable NCO-reactive compounds include polyether(poly)ols withbuilt-in tertiary nitrogen atoms which are preparable by propoxylationand/or ethoxylation of initiator molecules containing amine nitrogen.Such polyether(poly)ols are for example the propoxylation andethoxylation products of ammonia, ethanolamine, diethanolamine,ethylenediamine or N-methylaniline.

Other usable NCO-reactive compounds are polyester and polyamide resinswith tertiary nitrogen atoms, urethano-containing polyols with tertiarynitrogen atoms, and also polyhydroxypolyacrylates with tertiary nitrogenatoms.

The disclosed diisocyanates and/or higher functionalized polyisocyanatescan also be reacted with a mixture of nonionically hydrophilic-modifyingand cationically hydrophilic-modifying compounds, which are added insuccession or simultaneously, for example with a deficiency of thepolyethers VII and the aminoalcohols VIIl or the diamines IXa or IXb. Itis also possible to use mixtures of nonionically hydrophilic-modifyingand anionically hydrophilic-modifying compounds.

The recited types of cationically hydrophilic modified polyisocyanatesare more particularly described in DE-A 42 03 510 and EP-A 531 820.

Since the hydrophilic modified polyisocyanates (C) mentioned can ingeneral be used in aqueous media, adequate dispersibility of thepolyisocyanates must be ensured. Preferably, within the group of thedisclosed hydrophilic modified polyisocyanates, certain reactionproducts of di- or polyisocyanates and hydroxyl-terminated polyethers(polyetheralcohols) such as the compounds VII act as emulsifiers forthis purpose.

The good results which are obtained with the hydrophilic modifiedpolyisocyanates (C) in aqueous media are all the more surprising sinceit had to be expected that isocyanates would rapidly decompose inaqueous medium. Yet, the polyisocyanates used according to thisinvention have a "pot life" of several hours in the aqueous liquor; thatis, the instant polyisocyanate dispersions are stable during thecustomary processing time. A dispersion is said to be stable when itscomponents remain dispersed in one another without their separating intodiscrete layers. By "pot life" is meant the time during which thedispersions remain processible before they gel and set. Aqueousisocyanate dispersions gel and set because a reaction takes placebetween the water and the isocyanate to form a polyurea.

The mixtures of polyurethanes and isocyanates (D) are, like thecompounds (C), generally used in the process of this invention in theform of aqueous dispersions which are essentially free from organicsolvents and in most cases free from emulsifiers.

Polyurethanes are systems constructed from polyisocyanates (hereinafteralso known as monomers I) and polyisocyanate-reactive compounds havingat least one hydroxyl group and optionally compounds having at least oneprimary or secondary amino group. Polyurethanes generally do not containfree isocyanate groups.

Suitable polyisocyanates for preparing the polyurethanes present inmixtures (D) are customary diisocyanates and/or customary higherfunctional polyisocyanates of the type described in connection with thehydrophilic modified polyisocyanates (C). Here too aliphaticdiisocyanates and aliphatic higher functional polyisocyanates arepreferred.

The further formative components of the polyurethane are initiallypolyols having a molecular weight of from 400 to 6000 g/mol, preferablyfrom 600 to 4000 g/mol (monomers II).

Polyetherpolyols or polyesterpolyols in particular are suitable. Thepolyesterdiols are in particular the known reaction products of dihydricalcohols with dibasic carboxylic acids. Instead of the freepolycarboxylic acids, it is also possible to use the correspondingpolycarboxylic anhydrides or corresponding polycarboxylic esters oflower alcohols or of their mixtures for preparing the polyesterpolyols.The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic orheterocyclic with or without substitution, for example by halogen atoms,and/or unsaturation. Examples are succinic acid, adipic acid, subericacid, azeleic acid, sebacic acid, phthalic acid, isophthalic acid,phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalicanhydride, tetrachlorophthalic anhydride,endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleicacid, maleic anhydride, fumaric acid, dimeric fatty acids. Examples ofsuitable polyhydric alcohols are ethylene glycol, 1,2-propylene glycol,1,3-propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,4-butenediol,1,4-butynediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol,neopentylglycol, cyclohexanedimethanol(1,4-bishydroxymethylcyclohexane), 2-methyl-1,3-propanediol,1,5-pentanediol, also diethylene glycol, triethylene glycol,tetraethylene glycol, polyethylene glycol, dipropylene glycol,polypropylene glycol, dibutylene glycol and polybutylene glycols.

It is also possible to use lactone-based polyester diols comprisinghomo- or copolymers of lactones, preferably terminallyhydroxyl-substituted addition products of lactones or lactone mixtures,for example ε-caprolactone, β-propiolactone, γ-butyrolactone and/ormethyl-ε-caprolactone, on suitable difunctional initiator molecules, forexample the low molecular weight dihydric alcohols mentioned above asformative components for the polyesterpolyols. The correspondingpolymers of ε-caprolactone are particularly preferred. Similarly, lowerpolyesterdiols or polyetherdiols can be used as initiators for preparingthe lactone polymers. Instead of the polymers of lactones it is alsopossible to use the corresponding, chemically equivalent polycondensatesof the hydroxycarboxylic acids corresponding to the lactones.

The polyetherdiols, which are usable alone or else mixed withpolyesterdiols, are obtainable in particular by homopolymerization ofethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran,styrene oxide or epichlorohydrin, for example in the presence of BF₃, orby addition of these compounds, mixed or in succession, to initiatingcomponents having reactive hydrogen atoms, such as alcohols or amines,for example water, ethylene glycol, 1,3-propylene glycol, 1,2-propyleneglycol, 4,4'-dihydroxydiphenylpropane, aniline.

The proportion of the above-described monomer II is generally from 0.1to 0.8 gram equivalent, preferably from 0.2 to 0.7 gram equivalent, ofthe hydroxyl group of the monomer II based on 1 gram equivalent ofisocyanate of the polyisocyanate.

The further formative components of the polyurethane are chain extendersor crosslinkers having at least two isocyanate-reactive groups selectedfrom hydroxyl groups, primary or secondary amino groups.

Suitable representatives are polyols, especially diols and triols,having a molecular weight within the range from less than 400 g/mol to62 g/mol (monomers III).

More particularly, the above-recited diols and triols suitable forpreparing the polyesterpolyols and also more-than-trifunctional alcoholssuch as pentaerythritol or sorbitol are suitable.

The proportion of monomers III is generally within the range from 0 to0.8, in particular from 0 to 0.7, gram equivalent, based on 1 gramequivalent of isocyanate.

The optional monomers IV are at least difunctional amine chain extendersor crosslinkers of the molecular weight range 32 to 500 g/mol,preferably 60 to 300 g/mol, which contain at least two primary, twosecondary or one primary and one secondary amino group.

Examples thereof are diamines, such as diaminoethane, diaminopropanes,diaminobutanes, diaminohexanes, piperazine, 2,5-dimethylpiperazine,amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (isophoronediamine,IPDA), 4,4'-diaminodicyclohexylmethane, 1,4-diaminocyclohexane,aminoethylethanolamine, hydrazine, hydrazine hydrate or triamines suchas diethylenetriamine or 1,8-diamino-4-aminomethyloctane. Theamino-containing chain extenders can also be used in blocked form, forexample in the form of the corresponding ketimines (see for example CA-1129 128), ketazines (cf. for example U.S. Pat. No. 4,269,748) or aminesalts (see U.S. Pat. No. 4,292,226). Similarly, oxazolidines as used forexample in U.S. Pat. No. 4,192,937 are blocked polyamines which can beused for chain-extending the prepolymers in the preparation of thepolyurethanes of this invention. When such blocked polyamines are used,they are generally mixed with the prepolymers in the absence of water,and this mixture is then mixed with the dispersing water, or some of thedispersing water, so that the corresponding polyamines are formed asintermediates by hydrolysis.

Preference is given to using mixtures of di- and triamines, particularlypreferably mixtures of isophoronediamine and diethylenetriamine.

The optional monomers V for use as chain extenders are aminoalcoholshaving a hydroxyl and a primary or secondary amino group such asethanolamine, isopropanolamine, methylethanolamine oraminoethoxyethanol.

The proportion of monomers IV or V is in each case preferably from 0 to0.4, particularly preferably from 0 to 0.2, gram equivalent, based on 1gram equivalent of isocyanate of the polyisocyanate.

As further formative components, it is possible to use compounds havingat least one, preferably two, isocyanate-reactive groups, i.e. hydroxyl,primary or secondary amino groups, and also, unlike the above-describedmonomers, ionic groups or potentially ionic groups which can beconverted into ionic groups by a simple neutralization or quaternizationreaction (monomers VI). Incorporation of the monomers VI renders thepolyurethanes self-dispersible; that is, the polyurethanes disperse inwater without any need for dispersing aids such as protective colloidsor emulsifiers.

The cationic or anionic groups can be incorporated by using compoundshaving isocyanate-reactive hydrogen atoms and (potential) cationic or(potential) anionic groups. These groups of compounds include forexample polyethers having tertiary nitrogen atoms and preferably twoterminal hydroxyl groups, as obtainable for example by alkoxylation ofamines having two hydrogen atoms bonded to the amine nitrogen, forexample methylamine, aniline or N,N'-dimethylhydrazine, in aconventional manner. Such polyethers generally have a molecular weightwithin the range from 500 to 6000 g/mol.

Preferably, however, the ionic groups are introduced by usingcomparatively low molecular weight compounds having (potential) ionicgroups and isocyanate-reactive groups. Examples thereof are recited inU.S. Pat. Nos. 3,479,310 and 4,056,564 and also GB-1 455 554. Similarly,dihydroxyphosphonates, such as the sodium salt of ethyl2,3-dihydroxypropanephosphonate, or the corresponding sodium salt of theunesterified phosphonic acid, can be used as ionic formative component.

Preferred (potential) ionic monomers VI are N-alkyldialkanolamines, forexample N-methyldiethanolamine, N-ethyldiethanolamine,diaminosulfonates, such as the sodium salt ofN-(2-aminoethyl)-2-aminoethanesulfonic acid, dihydroxysulfonates,dihydroxycarboxylic acids such as dimethylolpropionic acid,diaminocarboxylic acids or diaminocarboxylates such as lysine or thesodium salt of N-(2-aminoethyl)-2-aminoethanecarboxylic acid anddiamines having at least one additional tertiary amine nitrogen atom,e.g. N-methylbis(3-aminopropyl)amine.

Particular preference is given to diamino- and dihydroxy-carboxylicacids, especially to the adduct of ethylenediamine with sodium acrylateor dimethylolpropionic acid.

The potential ionic groups which may be initially incorporated into thepolyaddition product are at least partly converted into ionic groups ina conventional manner by neutralization of the potential anionic orcationic groups or by quaternization of tertiary amine nitrogen atoms.

Potential anionic groups, for example carboxyl groups, are neutralizedusing inorganic and/or organic bases such as alkali metal hydroxides,carbonates or bicarbonates, ammonia or primary, secondary orparticularly preferably tertiary amines such as triethylamine ordimethylaminopropanol.

Conversion of the potential cationic groups, for example of tertiaryamine groups into corresponding cations, for example ammonium groups, iseffected using neutralizing agents comprising inorganic or organicacids, for example hydrochloric acid, phosphoric acid, formic acid,acetic acid, fumaric acid, maleic acid, lactic acid, tartaric acid oroxalic acid, or quaternizing agents comprising, for example, methylchloride, methyl bromide, methyl iodide, dimethyl sulfate, benzylchloride, chloroacetic esters or bromoacetamide. Further neutralizing orquaternizing agents are described for example in column 6 of U.S. Pat.No. 3,479,310.

This neutralization or quaternization of the potential ionic groups canbe effected before, during or preferably after the isocyanatepolyaddition reaction.

The amount of monomer VI is chosen with regard to the degree ofneutralization or quaternization of any components with potential ionicgroups and is suitably such that the polyurethanes contain from 0.05 to2, preferably from 0.07 to 1.0, particularly preferably from 0.1 to 0.7,meq of ionic group/g of polyurethane.

If desired, monofunctional amine or hydroxy compounds are also used asformative components (monomers VII). They are preferably monohydricpolyetheralcohols of the molecular weight range from 10 500 to 10000g/mol, preferably from 800 to 5000 g/mol. Monohydric polyetheralcoholsare obtainable for example by alkoxylation of monohydric initiatormolecules, e.g. methanol, ethanol or n-butanol, using an alkoxylatingagent comprising ethylene oxide or mixtures of ethylene oxide with otheralkylene oxides, especially propylene oxide. However, if alkylene oxidemixtures are used, these preferably comprise at least 40, particularlypreferably at least 65, mol % of ethylene oxide.

Through incorporation of monomers VII, the polyurethanes can thuscontain, in internal or terminal polyether chains, polyethylene oxidesegments which, alongside the ionic groups, influence the hydrophiliccharacter of the polyurethane and ensure or improve its dispersibilityin water.

The compounds of the type mentioned are preferred and preferably used insuch amounts that from 0 to 10, preferably from 0 to 5, % by weight ofpolyethylene oxide units are incorporated into the polyurethane throughthem.

Further examples of compounds usable as monomers I to VII in thepreparation of the disclosed polyurethanes are described for example inHigh Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", bySaunders-Frisch, Interscience Publishers, New York, London, Volume I,1962, pages 32 to 42 and pages 44 to 54, and Volume II, pages 5 to 6 and198 to 199.

Examples of suitable monomers VIII, which, unlike the foregoingmonomers, contain ethylenically unsaturated groups, include esters ofacrylic or methacrylic acid with polyols, in which case at least one OHgroup of the polyol remains unesterified. Of particular suitability arehydroxyalkyl (meth)acrylates of the formula HO(CH₂)_(m) OOC(R¹²)C═CH₂(m=2-8; R¹² =H, CH₃) and their positional isomers, mono(meth)acrylicesters of polyetherdiols, as recited for example in connection withmonomers II, trimethylolpropane mono- and di(meth)acrylate,pentaerythritol di- and tri(meth)acrylate or reaction products of epoxycompounds with (meth)acrylic acid, as mentioned for example in U.S. Pat.No. 357,221.

Of particular suitability are the adducts of (meth)acrylic acid withbisglycidyl ethers of diols, for example bisphenol A or butanediol.

It is also possible to use adducts of (meth)acrylic acid with epoxidizeddiolefins, for example 3,4-epoxycyclohexylmethyl3',4',-epoxycyclohexanecarboxylate.

Incorporation of monomers VIII makes it possible, if desired, tosubsequently cure the polyurethane thermally or photochemically, in thepresence or absence of an initiator.

In general, the proportion of ethylenically unsaturated groups is below0.2 mol per 100 g of polyurethane.

Altogether, the proportion of formative components is preferably chosenso that the sum of the isocyanate-reactive hydroxyl groups and primaryor secondary amino groups is from 0.9 to 1.2, preferably from 0.95 to1.1, based on 1 isocyanate group.

The preparation of the disclosed polyurethanes, especially in the formof dispersions, can be effected according to the customary methods asdescribed for example in the above-cited references.

Preferably, the monomers I and II and optionally III, V, VI, VII andVIII, if VI contains no amino groups, are reacted in an inert,water-miscible solvent, such as acetone, tetrahydrofuran, methyl ethylketone or N-methylpyrrolidone, to prepare the polyurethane or, iffurther reaction with amino-functional monomers IV or VI is intended, apolyurethane prepolymer still having terminal isocyanate groups.

The reaction temperature is generally within the range from 20° C. to160° C., preferably within the range from 50° C. to 100° C.

The reaction of the diisocyanates can be speeded up by using thecustomary catalysts, such as dibutyltin dilaurate, tin(II) octoate ordiazabicyclo(2.2.2)octane.

The resulting polyurethane prepolymer can be further reacted withamino-functional compounds of monomers VI and optionally IV at from 20°C. to 80° C., optionally after (further) dilution with solvents of theabovementioned kind, preferably with solvents having boiling pointsbelow 100° C.

The conversion of potential salt groups, for example carboxyl groups, ortertiary amino groups, which were introduced into the polyurethane viathe monomers VI, into the corresponding ions is effected byneutralization with bases or acids or by quaternization of the tertiaryamino groups before or during the dispersing of the polyurethane inwater.

After the dispersing, the organic solvent can be distilled off if itsboiling point is below that of water. Any solvents which have been usedwith a higher boiling point can remain in the dispersion.

The polyurethane content of the dispersions can be in particular withinthe range from 5 to 70 percent by weight, preferably within the rangefrom 20 to 50% by weight, based on the dispersions.

The dispersions may comprise customary assistants, for examplethickeners, thixotropicizers, oxidation and UV stabilizers or releaseagents.

Hydrophobic assistants which may be difficult to disperse homogeneouslyin the finished dispersion can also be added according to the methoddescribed in U.S. Pat. No. 4,306,998 to the polyurethane or theprepolymer before the dispersing.

Suitable isocyanates, the second component of mixtures (D), are inprinciple all compounds having at least one free isocyanate group.Particular importance here is possessed by the customary diisocyanates,the customary higher functional polyisocyanates, as described inconjunction with the hydrophilic modified polyisocyanates (C), and alsothe hydrophilic modified polyisocyanates themselves described under (C).However, monoisocyanates such as phenyl isocyanate or tolyl isocyanatesare also suitable.

The polyurethanes mentioned and the isocyanates mentioned are generallypresent in the form of mixtures in a weight ratio of from 10:90 to90:10, in particular from 25:75 to 75:25, especially from 40:60 to60:40.

In a preferred embodiment, compounds (D) comprise mixtures ofpolyesterurethanes and aliphatic diisocyanates, aliphatic higherfunctional polyisocyanates or hydrophilic modified polyisocyanates in aweight ratio of from 10:90 to 90:10.

Compounds (A) to (D) can generally be employed in aqueous system,preferably in aqueous solution or emulsion, in the novel process forpreparing cellulose fibers, in which case the aqueous system generallycomprises, based on the weight of the aqueous system, from 0.1 to 20% byweight, preferably from 0.5 to 10% by weight, of compounds (A) to (D).

Processes for producing solvent-spun cellulose fibers generally comprise4 steps.

Step 1: Dissolving the cellulose in a water-miscible solvent

Step 2: Extruding the solution through a die to form a fiber precursor

Step 3: Treating the fiber precursor with water to remove solvent andform the cellulose fibre

Step 4: Drying the fiber

The preferred solvent for step 1 is N-methylmorpholine N-oxide.

The wet fiber obtained in step 3 is never-dried fiber and generally hasa water content of from 120 to 150% by weight, based on the weight ofthe bone-dry fiber.

The water content of the dried fiber is generally from 60 to 80% byweight, based on the weight of the bone-dry fiber.

The novel treatment with compounds (A) to (D) can be effected either onthe wet fiber (during or after step 3) or on the dried fiber (after step4). However, a treatment at the fiber-forming stage (step 2), forexample in a coagulation bath, is also possible.

When the treatment is carried out on the wet fiber, this can be effectedfor example by adding the aqueous system of compounds (A) to (D) to acirculating bath comprising the fiber precursor. The fiber precursor canbe present in the form of a staple fiber, for example.

When the treatment is carried out on the dried fiber, this dried fibercan be present for example as staple fiber, web, yarn, knit or woven. Inthis case the fibers can be treated in an aqueous liquor, for example.

In contradistinction to the method described in EP-A-538 977, thepresence of alkali can be dispensed with in the process of thisinvention.

The treatment is generally effected at from 20° C. to 200° C.,preferably at from 40° C. to 180° C. In the course of the treatment, achemical reaction takes place between compounds (A) to (D) and thehydroxyl groups of the cellulose, which may also involve a chemical linkbeing formed between hydroxyl groups of different cellulose fibrils.This improves the stability of the fiber.

The treatment time is customarily within the range from 1 second to 20minutes, preferably within the range from 5 to 60 seconds, in particularwithin the range from 5 to 30 seconds.

In the case of impregnation, the treatment can be carried out not onlyat room temperature (20° C.) with subsequent drying at up to 100° C. butalso in the course of curing steps at up to 200° C., in particularwithin the range from 150° C. to 180° C.

The treatment of the wet or dried fiber can be effected with from 0.1 to10% by weight, preferably from 0.2 to 5% by weight, in particular from0.2 to 2% by weight, based on the weight of the bone-dry fiber, ofcompounds (A) to (D). However, in some cases it can also be advantageousto exceed the stated amounts, and use up to 20% by weight, for example.

The treatment may be carried out using further customary assistants incustomary amounts- A particular reference should be made here toantimigration agents, for example antimigration agents based onethoxylation products.

If compounds (A) and/or (B) are used for the purposes of this invention,the reactivity of these agents can be adapted to the processrequirements, i.e. generally raised, by addition of catalytic amounts ofLewis acids such as MgCl₂, ZnCl₂, AlCl₃, BF₃ or systems such as MgCl₂/NaBF₄ or MgSO₄ /NaBF₄ /LiCl or of inorganic or organic acids orcorresponding acid salts, for example HCl, H₂ SO₄, H₃ PO₄,p-toluenesulfonic acid, methanesulfonic acid, NaHSO₄, NaH₂ PO₄, (NH)₄HSO₄ or trialkylamine hydrochloride, or of other crosslinking inorganicsalts, for example nitrates or tetraalkylammonium salts.

As mentioned, compounds (A) to (D), unlike the compounds described inEP-A-538 977, can be fixed purely thermally (without alkali), makingthem convenient to integrate in the fiber

We claim:
 1. A process for producing solvent-spun cellulosic fibershaving a reduced tendency to fibrillate, which comprises treating thefibers with one or more compounds selected from the group consistingof1) hydrophilic modified polyisocyanates; and 2) mixtures ofpolyurethanes with isocyanates.
 2. The process of claim 1, whereincompounds (1) are nonionically hydrophilic modified polyisocyanatescontaining hydroxyl-terminated polyethers of the formula (VII):

    R.sup.8 --E--(DO).sub.n --H                                (VII)

wherein R⁸ is C₁ -C₂₀ -alkyl, C₂ -C₂₀ -alkenyl, cyclopentyl, cyclohexyl,glycidyl, hydroxyethyl, phenyl, tolyl, benzyl, furfuryl ortetrahydrofurfuryl; E is sulfur or oxygen; D is propylene or ethylene;and n is from 5 to
 120. 3. The process of claim 1, wherein compounds (2)are mixtures of polyesterurethanes and aliphatic diisocyanates,aliphatic higher functional polyisocyantes or hydrophilic modifiedpolyisocyantes in a weight ratio of from about 10:90 to 90:10.
 4. Theprocess of claim 1, wherein the fibers are treated with from 0.1 to 10%by weight of compounds (1) to (2) based on the dry weight of the fibers.5. The process of claim 1, wherein the treatment is carried out at fromabout 20° to 200° C.
 6. The process of claim 1, wherein said hydrophilicmodified polyisocyanates are based upon aliphatic diisocyanates,cycloaliphatic diisocyanates, aromatic diisocyanates or polyisocyanateshaving a functionality of greater than two.
 7. The process of claim 6,wherein said aliphatic diisocyanates are selected from the groupconsisting of tetramethylene diisocyanate, hexamethylene diisocyanate,octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylenediisocyanate, tetradecamethylene diisocyanate, trimethylhexanediisocyanate and tetramethylhexane diisocyanate.
 8. The process of claim6, wherein said cycloaliphatic diisocyanates are selected from the groupconsisting of 1, 4-, 1, 3-, 1, 2-diisocyanatocyclehexane, 4, 4'-di(isocyanatocyclohexyl) methane, 1-isocyanato-3, 3,5-trimethyl-5-(isocyanatomethyl cyclohexane, 2, 4- and 2, 6-diisocyanato-1-methylcyclohexane.
 9. The process of claim 6, whereinsaid aromatic diisocyanates are selected from the group consisting of 2,4-, 2, 6- tolyene diisocyanate, p-xylylene diisocyanate, 2, 4'-, 4,4'-phenylene diisocyanate, 1, 5-naphthylene diisocyanate, diphenylene 4,4'-diisocyanate, 4, 4'-diisocyanato-3, 3'-dimethyldiphenyl,3-methyldiphenylmethane 4, 4'-diisocyanate and diphenyl ether 4,4'-diisocyanate.
 10. The process of claim 6, wherein saidpolyisocyanates having a higher functionality than two are selected fromthe groups consisting of 2, 4, 6-triisocyanatotoluene, 2, 4,4'-triisocyanatodiphenyl ether and mixtures of tri- and hipherpolyisocyanates which are obtained by phosgenation ofaniline/formaldehyde condensates and are methylene-bridged polyphenylpolyisocyanates.